Explanations:

Each molecule of NaCl contains one sodium ion and one chloride ion. Therefore, 3.0 moles of NaCl contains 3.0 moles of sodium ions.

$$(3.0 \text{ mol NaCl})(6.022 \times 10^{23} \text{ Na}^+ \text{ ions/mol NaCl}) = 1.81 \times 10^{24} \text{ Na}^+ \text{ ions}$$

Therefore, there are 1.81 x 10^24 sodium ions in 3.0 moles of NaCl.